Tensei Saki ga Kiyowa Sugiru Hakushaku Fujin datta

Lam Mercure has always led a miserable life. Due to her cowardly nature, she spent her childhood ridiculed by her family, and things only got worse when she became the second wife of Char, the Earl of Mercure. Char is a busy mage who’s perpetually absent from the estate, leaving Lam to fend for herself—and his servants take every chance to torment the poor countess, fully aware she is too timid to retaliate...until something unexpected happens. While being bullied by her handmaidens, Lam hits her head and regains the memories of a past life—five hundred years ago, she was Aurora, the strongest witch in history! Now that she remembers her true self, Lam won’t live as a victim any longer. With her reawakened powers, she’ll punish the servants, talk back to her husband, and reclaim her freedom—on her own terms!

[From J-Novel Club]